Certain neurotransmitters, hormones or paracrine agents are known to be secreted into the lumen of the gut and to alter gut absorption, blood flow or motility from the lumen in the same or a different manner as when applied to the interstitial surface. The mechanisms of actions are largely unknown as is the extent of the substances which have luminal effects. The aim of this research proposal is to contrast the effects of acetylcholine, serotonin, pentagastrin, secretin, morphine (as an enkephalin analogue) and prostaglandin E1 when perfused intraluminally or intraarterially. Effects on net and unidirectional Na and H2O fluxes, total and regional blood flow and motility will be measured in canine ileum. The possibility of extrinsic nerve reflexes being involved in these effects will also be evaluated. The ultimate goal of these experiments is to determine if intraluminal effects of certain agents have physiological or pathalogical significance.